Parking assistance systems may be incorporated into a motor vehicle with a motoring unit for sensing an object in the vicinity of the motor vehicle, e.g. on the basis of radar signals, and a signal emitter controlled as a function of the results of a sensed object are generally known. The signal emitter can be a display on which the position of the object relative to the motor vehicle and its distance therefrom is visualized, in addition an acoustic signal emitter may be provided. From this information, the driver can estimate the distance from the object, irrespective of the direction in which he or she is looking.
DE 10 2009 058 034 A1 describes a parking assistance system with a monitoring unit which can also continue to be operated after completion of the parking in order to monitor, on the parked motor vehicle, the approach of other motor vehicles to the parked motor vehicle, and a lamp, which is controlled by the monitoring system to warn the driver of such another motor vehicle by way of a light signal of a critical approach.
The beeping sounds used as acoustic warning signals by most conventional parking assistance systems are considered as unpleasant or annoying by many users, particularly if the sound level is poorly adapted to the noise level of the surroundings. If a driver who feels annoyed by the signals of a conventional parking assistance system turns down its sound level, there is the risk that when the motor vehicle is subsequently driven by another driver who is not aware of the reduced sound level, this driver may not hear the signals and thus presumes that there is no obstacle in the way.
A further problem is that the acoustic signals used usually have a high frequency in order to be easily perceived by a driver with normal hearing against a background of engine sounds at lower frequencies, but drivers with a degree of hearing loss may find such signal difficult to discern.